Deciphering correct wiring for 3 way/4 way switches

Reply

  #1  
Old 09-07-06, 08:59 PM
Member
Thread Starter
Join Date: Nov 2001
Location: usa
Posts: 417
Received 1 Vote on 1 Post
Deciphering correct wiring for 3 way/4 way switches

I changed some old 3 way (Two in total) & one 4 way switch on the same circuit to modern decora types. Though it seems to be working correctly I'd like to be sure I wired things correctly. Unfortunately when I read about the"correct" way to wire such circuits the old wiring doesn't seem to follow the modern standard leaving me somewhat confused.

Basically the circuit appears as follows:

One 3 way switch with Red attached to Common & two Black wires attached to travelers, One 4 way switch with two reds & two blacks attached & finally one 3 way switch with a white , red & black wire in the box - Unfortunately the old switch was not marked to indicate common & had no screws just backfed wiring. I wired the replacement for this switch with the white as the common & the red & black as travelers and everything seems to work fine but I'm not sure its correct.

I would have thought the first switch should have had the black as the common but that was not how the old one was wired so I just replaced it same as the old one. Regarding the last switch - I assume its at the end of the run given the fact that there's a red , white & black in it. Needless to say I somewhat confused.

Using a tester of sorts how can I figure out where each switch lies in the circuit in relation to eachother, the fixtures & the power source? This would help in sorting out how the old wiring was run & determining what should go where. Thanks
 
Sponsored Links
  #2  
Old 09-08-06, 12:06 AM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
Received 0 Votes on 0 Posts
I've seen these switches from different manufacturers have the common screw in a different place in relation to the travelers' screws.

You may want to verify what you can about the first switch, but if it's working, it's working. Verify by trying each combination of switches and seeing the the lights toggle every time any switch is thrown.
 
  #3  
Old 09-08-06, 04:36 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Received 0 Votes on 0 Posts
As Mac stated, screw/terminal position means nothing. Different manufacturers pout the terminals in different locations. Youn have to go by terminal color and/or a wiring diagram for the switch.

Electrically speaking, the three way switches are the end, and the four way switches (and there can be any number of these) are in the middle. However, without testing (or visible confirmation) you cannot tell which three way has an always hot common wire and which three way has a switched hot common wire.

Further, if the light is in the middle somwehere or if there is some other junction box in the middle, then wire color doesn't mean much.

First, and most important, with three switches there are eight ways the switches can be positioned (down-down-down, down-down-up, down-up-down, down-up-up, up-down-down, up-down-up, up-up-down, and up-up-up).

Just verify that the light is on for half of these and off for the half, and that you can turn the light on and off at any time from any of the three switches.

However, if you want to test, use your tester and figure out the always hot common wire. It will be at one of the three way switches. Then go to the four ways switch and figure out which two travelers come from the first three way switch. Then figure out the travelers at the last three way switch. Just look for power on the wires.
 
  #4  
Old 09-08-06, 06:42 AM
Member
Thread Starter
Join Date: Nov 2001
Location: usa
Posts: 417
Received 1 Vote on 1 Post
What is the best way to test for the always "hot" common wire?

If then switches work correctly & as you say the lights are on for half of the switch positions & off for the other half of the switch positions does that imply the wiring is correct?
 
  #5  
Old 09-08-06, 06:47 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Received 0 Votes on 0 Posts
To test for the always hot common wire, use a two wire tester and test between each wire and ground. The always hot wire will be the wire that turns the light on.

You should test with the wires NOT connected to the switch.

You must be able to turn the lights on and off from any loacation with the switches in the other two locations in any of the four possible combinations.
 
  #6  
Old 09-08-06, 11:12 AM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
Received 0 Votes on 0 Posts
Originally Posted by bvgas
What is the best way to test for the always "hot" common wire?
My answer is different than Bob's. I feel the best way is with a non-contact voltage tester, like a Fluke AC-1 (the best), or even the Greenlee that they sell at Home Depot (though it tends to give more false alarms at times in other situations.)

Separate all wires at all switches (this is done with the power off.) When all wires are separated from one another and sticking out of the box, turn the power on. Only one wire will cause the tester to glow.

You MIGHT also be able to start with a guess. Many times the 3-way that is closer to the fixture is the switched common, but this is only a starting guess, never rely on it.
 
  #7  
Old 09-08-06, 12:09 PM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 6,707
Received 77 Votes on 71 Posts
If everything works you probably got it correct.. Where do the wires for the light and power connect into this? It sounds like you might have a minor code voilation with the white wire on the common screw.
 
  #8  
Old 09-08-06, 01:40 PM
Member
Thread Starter
Join Date: Nov 2001
Location: usa
Posts: 417
Received 1 Vote on 1 Post
Thanks for all the replies:

In terms of testing for the "hot" wire - can I use the electrical box as the ground? I find when I often do this I don't always get reliable info.

The reason I hooked the white to the common is it seemed to make the most sense being that I figured the 4 way switch must be before that 3 way switch in the circuit (And by the presence of only one cable with a red, black & white wire in the box that that switch must be at the end of the circuit) & I figured since a red & black were "travelers" coming from it I attached them to the traveler screws on the 3 way leaving the white to go to the common. As I mentioned earlier the prior old 3 way switch had no markings or screws to indicate the "common".

In terms of trying to reason this out I would assume the 3 way switch with the two blacks & one red is first in the circuit followed by the 4 way switch & finally the 3 way switch with red, black & white. If this is the case it seems to me that on this first 3 way switch one of the other black wires should enter the common not the red, leaving a black & red as travelers. The reason I think this is that the 4 way switch which should be somewhere in between both 3 ways has a black & red going in, and a black & red going out. However I simply duplicated the old wiring regarding the red going to the common & everything seems to be working correctly. Perhaps as racraft said the colors in old wiring might not mean much & is what's throwing me off. Is my above reasoning correct??
 
  #9  
Old 09-08-06, 02:08 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Received 0 Votes on 0 Posts
Wire color always is important, and so is screw color. However, travelers can be swapped at will with each other on a three way circuit and on the same electrical side of a four way switch.

It is a code violation to connect a white wire to a common terminal on a three way switch. This is a minor code violation, but is one nevertheless.

When replacing switches in a setup like yours, you can (and a novice should) replace one switch at a time, and verify proper operation after each switch is installed. If it worked properly BEFORE the new switches, it should still work properly after each and every switch is replaced. If you test thoroughly after each switch is installed, and if you find a problem, it will be at the switch you just installed.

I agree that in your assumption on which switches being first, second and third, but it is irrelevant. A three way switch is always first, four way switches are in the middle, and a three way switch is always last.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: